In a milling operation, many cutting edges are generally mounted on the side surface of a milling cutter to machine a work piece. Thus, the machining performance varies remarkably depending on the depth of cut and the shape of a cutting insert.
Due to improvements in milling machines, high speed and high feed machining is available. To improve productivity, such machines have been adopted and a method of removing large chips at once with a deep cut is generally used.
In such a milling operation, if the cut is deep, then the cutting resistance is greatly increased. Thus, if the milling machine with a small horse power is excessively operated under the above-mentioned conditions, then the main axis of the milling machine or table may be damaged. Further, this causes vibration and noise, thereby decreasing machining accuracy and tool life.
To overcome such problems, a cutting insert, the cutting edges of which are divided by recesses to reduce cutting resistance, has been known. FIG. 1 shows a conventional cutting insert. As shown in FIG. 1, cutting edges 2 of a cutting insert 1 are divided by a plurality of recesses 3. The recesses are formed to have 180 degree rotational symmetry about a through hole 4 formed at the center of the cutting insert. Further, as shown in FIG. 2, the cutting inserts 1 are mounted on the side of the milling cutter.
In a milling operation, a work piece is first cut by the cutting insert 1, which has four recesses. The part of the work piece, which is not cut due to the recesses 3 of the cutting insert 1, is then cut by a following cutting insert 1′ that has three recesses.
As such, in the conventional milling operations, two types of cutting inserts, which have different recesses from each other, are manufactured and stored. This tends to increase maintenance costs as well as manufacturing costs. Further, having two types of inserts creates the possibility that an operator may not mount the two different cutting inserts in turn and may instead erroneously mount two of the same type of cutting inserts.